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S15 weather shields installation tips?

I've just got some Nissan weather shields for my S15 and I just wanted to check on here if anyone knows of a installation guide or has any tips and tricks for the install and what are the pitfalls to look out for?
I read somewhere that it's easier to remove the trim on the car first and install the weather shield onto the trim then install the trim back on the car?
Any useful advice is appreciated.